In normal NREM sleep phase, the basal tone of upper airway muscles decreases, upper airway caliber decreases, and airway resistance increases, but the firing phase of upper airway muscles and the rhythmic contraction of intercostal muscles remain intact. during REM sleep, the basal tone of upper airway muscles, intercostal muscles, and most skeletal muscles are further suppressed. The reduced tone of the pharyngeal muscles can cause trapping of the upper airway during inspiration. What are the causes of upper airway trapping during inspiration: Normal breathing requires a high degree of coordination of respiratory muscle contraction. The upper airway muscles have some basic tone to keep the airway open. Before each diaphragmatic contraction, the nerve discharge causes the upper airway muscles to contract. Contraction of the chin-lingual muscle pulls the tongue forward to fix the pharyngeal wall, further keeping the upper airway open and resisting the trapping effect of negative pressure in the pharyngeal cavity on the upper airway during inspiration. Subsequently, the intercostal muscles contract to stabilize the chest wall, and the diaphragm contracts to generate negative thoracic pressure to complete inspiration. In normal NREM sleep phase, the basal tone of the upper airway muscles decreases, the upper airway caliber decreases, and airway resistance increases, but the firing phase of the upper airway muscles and the rhythmic contraction of the intercostal muscles remain intact. during REM sleep, the basal tone of the upper airway muscles, intercostal muscles, and most skeletal muscles are further suppressed. Reduced tone of the pharyngeal muscles can cause trapped closure of the upper airway during inspiration. Hypotonia of the chin-lingual muscles can cause posterior displacement of the tongue root and airway narrowing. Hypotonia of the intercostal muscles can lead to chest wall instability during inspiration, producing paradoxical thoracoabdominal movements. In the REM sleep phase, the inspiratory-phase discharge of the upper airway and intercostal muscles can also be inhibited, and the tendency to trap the upper airway and chest wall instability is exacerbated when the negative thoracic pressure increases after diaphragmatic contraction. Sleep disorders: Common non-organic sleep disorders in psychiatry are non-organic sleep and wake disorders caused by various psychosocial factors. Insomnia is a condition of sleep quality dissatisfaction with insomnia as the main cause, and other symptoms are secondary to insomnia, including difficulty falling asleep, poor sleep, easy waking, excessive dreaming, early waking, difficulty falling back asleep after waking, feeling unwell after waking, fatigue or daytime sleepiness. Insomnia can cause apprehension or fear in patients and lead to decreased efficiency in mental activities and impede social functioning. Chronic sleep disorders can affect up to 15% of the adult population. The broad definition of sleep disorders should include insomnia from various causes, excessive sleepiness, sleep breathing disorders, and abnormal sleep behavior, the latter including sleep walking, sleep panic, and restless legs syndrome.